Lord Lentilux fiddled with various lenses and then said "This may be close to what you need. Tell me what you can see now, first with each eye on its own and then with both eyes together"
The young lady took a good, long look and said "This is strange. My vision is not good with each eye on its own, but quite good with my two eyes together. How come?"
"That's a bit of a technical story but I'll try to explain it. I expected that you have astigmatism, which means that your eyes are probably more shortsighted in the vertical direction and less shortsighted in the horizontal direction. Many people have astigmatism, myself included. The lenses in this pizza box are not for the correction of astigmatism so I used a trick instead. Optician often use it for soft contact lenses. One eye gets the prescription with the minimal value, the other eye gets the maximal value. And your brain is able to combine both images into one good image"
"How bad is my eyesight?"
"These lenses are -1.75 and -2.50. Not too bad but you do need glasses. I can measure more precisely with the lenses for astigmatism. They are in my hotel room, just one block away"
"I would like to see my looks in glasses with this prescription. Do you have any of those with you?"
"Not in this pizza box. Perhaps in the hotel. Can you allow me ten minutes to go checking?"
"Yes, of course. It's so much nicer to sit and wait on this beach than it is in a shop"
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